Water heater device with heat and water recovery

ABSTRACT

A system for rapid and efficient water heating is provided, with a water and heat recovery component. Using a thermal store as a heat exchanger the system mixes steam and cold water to deliver hot water at a user-controlled temperature. The high operating temperature of the thermal store and its thermal efficiency result in a compact, highly-efficient means of hot water delivery. Water and energy usage are further reduced through a means of recycling hot water through the system in operation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/587,692 filed on Jan. 18, 2012 and U.S. Provisional PatentApplication No. 61/639,128 filed Apr. 27, 2012, both of which areincorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention is in the field of fluid heating, moreparticularly a system designed for instantaneous water heating across arange of temperatures and at variable flow rates.

BACKGROUND OF THE INVENTION

Hot water has myriad uses such as domestic heating, washing and foodpreparation. Numerous solutions are available based on a variety oftraditional power sources such as electricity, oil and gas as well asnewer technologies such as solar, geothermal and heat pumps. Aside fromthe power source, there are numerous options depending on theapplication, such as tanked systems which heat and store water asrequired, to instantaneous systems which heat water on demand. Each ofthese options has its own characteristics and constraints such as size,power consumption, installation complexity and maintenance requirements.

Several factors are driving innovation in the hot water arena, includingthe increasing importance of energy efficiency, cost of water supply,lower carbon emissions and the demand for compact, easily-installed, lowmaintenance products.

Recovery of treated water is well known in the art. A typical example is“greywater”, where used water from sources such as showers, baths andhand basins is recycled, often close to the original point of use, e.g.in a household. Such greywater is usually utilised for flushing toiletsor soil irrigation. There are difficulties associated with using thiswater in applications such as washing and bathing, includingpurification and filtration issues, to the extent that its use is notpermitted in domestic situations in many jurisdictions.

SUMMARY OF THE INVENTION

The invention disclosed herein provides a water heater system designedto deliver hot water at a constant, user-selectable temperature with avariable flow rate. In addition, it incorporates a heat and waterrecovery component designed to capture the waste hot water after itsinitial application (for example, a domestic shower) and reuse both thewater itself and the heat energy contained therein, feeding both backinto the main system, thus reducing overall water and energy usage.

The system is composed of a thermal store used as a heat exchanger and acold water-to-steam mixer element. A cold water supply is heated as itenters the heat exchanger within the thermal store. Since the thermalstore operates at high temperatures, this flow of water is turned intosteam as it goes through it. The steam is then mixed with cold water.The set temperature is achieved by varying the mix ratio of steam andcold water.

The recovery component of the system incorporates an inlet feed to takethe used water. This water will need purification and reheating beforeit can be reused and this is achieved by passing the water through thethermal store. The amount of heat energy that can be reused is dependenton a number of factors, including the desired output temperature andtemperature drop during use.

The thermal store operates typically between 450-900 degrees Celsius.Due to this high operating temperature and the consequent amount ofthermal energy held, large volumes of hot water can be provided whilereducing the size of the thermal store compared to traditional,tank-based stores. Another benefit of this implementation is thatoperating at over 850 degrees Celsius prevents water scaling aslimescale cannot form at this temperature. Additionally, the hightemperature serves to purify the waste water being fed back into thesystem to ensure its suitability for re-use. The heat contained withinthis recycled water reduces the overall energy needed for the thermalstore to provide hot water at the required temperature.

Even though the temperature of the thermal store is higher thantank-based stores, the heat losses will be minimized because the thermalstore is a lot smaller than normal stores thus reducing the overallsurface area of the system and insulation can be applied moreefficiently.

The thermal store is a metallic item heated up to a high temperature.The upper limit of the temperature is dependent on the material used.The volumetric heat capacity of the material used will define theoverall volume of the system. High thermal conductivity is a desirablefeature of the material used for the thermal store to optimize the heattransfer from the store to the water. Very favorable results areachieved with a material that has a high volumetric heat capacity and ahigh thermal conductivity such as iron and steel.

The thermal store can also include any phase change of the material thatwill give even more energy stored for the same volume such as moltenmetals or salts. If this method is used, the material to which the phasechange occurs will be encapsulated in a high thermal conductivitymetallic casing.

The thermal store has holes through which water can enter and be turnedinto steam before exiting the heat exchanger. The space between theholes is defined by the thermal conductivity of the material used. Thehigher the thermal conductivity of the material, the larger the spacebetween the holes.

The volumetric size of the thermal store is defined by the type ofmaterial used such as steel and the quantity of hot water and itssupplied temperature that the device has been designed to provide andthe amount of used, hot water that can be recycled and its heat energywhen it enters the thermal store after initial use.

The metallic thermal store can be heated to its selected operatingtemperature in a number of different ways. The most common way is to useresistive elements such as cartridge heaters. It can also be heated upby electromagnetic induction. In addition fuels such as gas or oil canbe used to heat the thermal store due to its construction and operation.

The water output of the heater is non-pressurized where input and outputwater pressures are required to remain the same or pressurized in acontainment vessel where a controlled output water pressure is required.

To achieve the required water temperature, the steam is mixed with coldwater. This can be done in different ways; for example using a sparger,injecting the steam into a tank of cold water, using a heat exchanger orwith a mixing valve.

Advantages of the system according to the disclosure include, systemmaterial requirements and weight are significantly less than a tankedsystem delivering comparable water volumes, and the surface area of thethermal store relative to that of a tank necessary to store water at adesired temperature is substantially lower leading to greatly reducedthermal losses. Further, the energy in the thermal store rapidly heatsthe cold water input thus reducing waiting time for uses requiring largevolumes of hot water delivered over a short timeframe, and the highoperating temperature of the system means that lime scale cannot buildup in the heat exchanger, thus enhancing system life cycle even whenutilised in hard water environments. Still further, no solid to liquidphase change needs to be employed hence there is no risk of the escapeof high temperature fluid or any possibility of changes to thereversibility of the charge, discharge cycle. The high operatingtemperature of the system means that any harmful bacteria present in thewaste water being recycled or run through the system are eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, referenceis now made to the following description taken in conjunction with theaccompanying drawings.

FIG. 1 is a perspective view of a heat exchanger core of a systemaccording to the disclosure, partially in phantom, with attachedmanifold plates and associated pipework;

FIG. 2 is a cutaway drawing of the steel core of the heat exchanger;

FIG. 3 is a perspective view of the manifold plates of the heatexchanger;

FIG. 4 is a view of the heat exchanger fitted with cartridge heaters andthermocouple;

FIG. 5 is a schematic diagram of the system;

FIG. 6 is an assembly view of the system; and

FIG. 7 is a view of the sparger used in mixing the steam and cold water.

DETAILED DESCRIPTION

In accordance with one embodiment of the present invention illustratedin FIGS. 1 and 2, a heat exchanger 10 is provided. As described, theembodiment is illustrative and the dimensions indicated are approximateand may differ in alternative embodiments. At its center is a steel core100. The steel core is, for example, of medium carbon steel EN8 and is135 mm wide, 135 mm deep and 100 mm tall. Within the steel core are anumber of cylindrical holes as illustrated in FIG. 2. In thisillustrative embodiment, there are eight holes 103 in a 4-4 patternrunning horizontally through the core from side to side and eight holes104 in a 3-2-3 pattern running vertically from top to bottom through thecore. The horizontal holes are 12.7 mm in diameter and arranged in tworows. The upper row has the hole centers 27.5 mm from the core's top andat 22.5 mm, 52.5 mm, 82.5 mm and 112.5 mm on the side face. The lowerrow has the hole centers 72.5 mm from the core's top and the same as theupper row with respect to the side face.

Positioned adjacent to one of the horizontal holes is a hole 105 whichis 1.5 mm in diameter and 60 mm deep, with its hole center at 82.5 mmfrom the side and 35.6 mm from the top intended to hold a thermocouple110. The thermocouple may be a K-Type, model XQ-182-RS supplied byRadionics Limited, part of Electrocomponents plc of Oxford, UnitedKingdom. The three columns of vertical holes in the core are arranged asfollows: Columns 1 and 3 each comprise three holes with their centers at32.5 mm, 67.5 mm and 102.5 mm from the side face. Column 2 has twoholes, with their centers at 50 mm and 85 mm from the side face. Allholes are 13 mm in diameter.

Welded to the top and bottom of the core are two manifold plates 101,102. These plates are centered on the top and bottom of the steel core,thus substantially completely covering the eight vertical holes 104running through the core. The plates, as illustrated in FIG. 3, are ofstainless steel grade 304 and are 97 mm in width and depth and 20 mmtall. There is a recess 115 inside the plates which is 80 mm square and18 mm deep, leaving a border 120 of 5 mm around the edge. It is thisborder which is welded to the steel core. At the center of each manifoldplate is a hole 125 of 15 mm diameter. Welded to the hole in eachmanifold plate is a grade 304 stainless steel pipe 130, 135 which act asthe water inlet (on the bottom of the steel core) and steam outlet (onthe top of the steel core). They are 15 mm in diameter, 2 mm thick and60 mm in length. The end of each pipe is equipped with a threaded boss140, 145 for connection to inlet and outlet pipework.

As shown in FIG. 4, each of the eight horizontal holes in the steel coreis fitted with a cartridge heater 150. These are, for example, suppliedby Watlow, of St. Louis, Mo., USA, model HT Firerod, which have amaximum operating temperature of 982 degrees Celsius.

Each of the cartridge heaters is connected to a controller 155. In thisembodiment a Series 122 Bare Board controller from Zytron ControlProducts of Trenton, N.J., USA is utilised to manage the operatingtemperature of the system. Power for the system is fed through thecontroller, in this case a typical 240V mains supply. This board is alsoconnected to the thermocouple 110 located within the steel core as partof the control mechanism. A schematic diagram of the system is providedin FIG. 5. Once switched on, the heat exchanger is initially heated to atemperature of 850 degrees Celsius. The controller then shuts off thecartridge heaters and monitors the temperature of the system. When thetemperature of the heat exchanger (either as a result of standing lossesover time or from water being passed through) drops below a presetthreshold, for example 95% of its initial temperature, the controllerswitches on the cartridge heaters until the system is restored to fulltemperature.

Ultimately, the output water temperature of the system is dictated bythe ratio of steam to cold water. In this embodiment two proportionalflow gate valves 160, 165 as shown in FIGS. 5 and 6 are used to managethis ratio. These are manually controlled but could equally beelectronic and linked to a user-controlled output temperature setting toautomatically adjust the output temperature. By controlling the flow ofwater to the heating block, the amount of steam produced can becontrolled and consequently the output water temperature of the system.When a user wishes to operate the system, they press the switch 164.

Connected to the system through pipe 135 is a source of cold water, forexample a main water supply. This water supply is subsequently splitinto two paths 170, 175 as shown in FIGS. 5 and 6. A first flow 170 isdirected into the heat exchanger 10. It flows into the manifold plate102 and up through the eight vertical channels 104 in the heatexchanger. The 850 degree temperature of the heat exchanger converts thewater to steam which passes out of the exchanger through the manifoldplate 103 and pipe 140. It then passes through a check valve 190 (toprevent the cold water in the mixer from entering the heat exchanger)and enters the mixer 180. A second flow 175 is directed through astandard ½ inch pipe through gate valve 165 into the mixer.

The mixer essentially consists of a mixing junction for steam from theheat exchanger and cold water from the second water flow 175. Containedwithin it is a sparger 200 to provide for an efficient mix of the steamand water. The sparger is illustrated in FIG. 7. In this illustrativeembodiment it is 71 mm long and cylindrical in shape over 51 mm of itslength with a diameter of 6 mm, with a shoulder over its remaining 20mm. The shoulder has a threaded end to allow it to be connected insidethe mixer in conjunction with a reducer sleeve. Beginning 8 mm from theshoulder and situated along the cylindrical section are 6 rows of 8holes, spaced 4.53 mm apart, giving a total of 48 holes, each ofdiameter 1.5 mm. Two solenoid valves 161, 162 are fitted in the systemand electrically linked to the push button switch 164 shown in FIG. 5.Also installed is a pipe 167 which feeds the hot waste water which wasoriginally discharged through the solenoid valve 162 back to the systemat a point after the cold water supply 135 but before the proportionalflow gate valve 160, with a check valve fitted as necessary to preventthis water flowing back into the second water flow 175. This water maybe collected from a standard waste system installed for collection anddisposal of the hot water originally discharged through the valve 162.Given that the water entering the system through inlet 167 will behotter than that entering through the supply pipe 135 the overall energynecessary to heat the water flowing through the heat exchanger 10 isreduced relative to a system where only the cold water from supply 135is utilised. Electronic controls incorporating necessary temperaturesensors for the proportional flow gate valves 160, 165, while not shownin this illustrative embodiment, are well known in the art and could bereadily incorporated.

Once the steam and water have mixed, the resulting hot water flows intoa reservoir tank 210 through a ½ inch copper pipe. The tank isconstructed from 304 gauge stainless steel and is 205 mm high, 100 mmwide and 50 mm deep. It is provided with fittings to take the outputfrom the mixer, installation of an air bleed valve 163 and an outputthrough the second solenoid valve 162. In an alternative embodiment, thetank may not be incorporated and the hot water may be drawn off directlyfrom the mixer.

The heat exchanger 10, exposed pipework and the tank 210 are all coveredin high-performance insulation, in this embodiment Promalight 320 byPromat UK of Bracknell, United Kingdom.

Pumps are well known in the art, used for a variety of reasons includingpoor mains pressure, plumbing constraints where a water tank is belowthe desired delivery point, specific application requirements such aspower showers, and so on. In a further illustrative embodiment, thesystem, when equipped with the tank 210 can also provide pressurised hotwater, thus eliminating the need for a separate pump. A pressure gaugeincorporated into the system in the tank 210 permits user-controlleddelivery pressure by varying the amount of steam in the tank thuscausing a pressure build-up. Standard mixing valves and aperture controlallow for the user to select the desired pressure at the delivery point,the upper limit bounded by choice of materials and consequent operatingparameters.

While the invention has been described with reference to illustrativeembodiments, it will be understood by those skilled in the art thatvarious other changes, omissions, and/or additions may be made andsubstantial equivalents may be substituted for elements thereof withdeparting from the spirit and scope of the invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teaching of the invention without departing from the scope thereof.Depending on particular regulations or requirements, it may be desirablefor all water-contacting surfaces to be made from copper or stainlesssteel, for example. The temperature range available to the user and thevolume of hot water supplied by the system may be varied. The powersource used to heat the thermal store is not limited to any one type.Further, while a metallic thermal store is described, those skilled inthe art should appreciate that other materials that withstand extremetemperature could be implemented, such as any of various compositematerials. The system may be utilised in a variety of situations whereinstant, clean, efficiently-delivered hot water is desirable, such aspersonal showering, hand washing, and the like. Therefore, it isintended that the invention not be limited to the particular embodimentdisclosed for carrying out this invention, but that the invention willinclude all embodiments, falling within the scope of the appendedclaims.

What is claimed is:
 1. A water heater system, comprising: a thermalstore receiving fluid for heating; a heat exchanger integrated withinthe thermal store to receive the fluid and heat the fluid to provideheated fluid; a steam-cold fluid mixer receiving the heated fluid andmixing the heated fluid with a lower temperature fluid to provide atemperature regulated fluid, the temperature of the temperatureregulated fluid being a function of the temperature of the heated fluidand the lower temperature fluid.
 2. The water heater system of claim 1wherein the fluid received by the thermal store is water and the heatedfluid provided by the heat exchanger is steam.
 3. The water heatersystem of claim 2 wherein the water heater system further comprises ahot water/steam output apparatus.
 4. The water heater system of claim 1further comprising an electronic controller controlling the heatexchanger and steam-cold fluid mixer.
 5. The system of claim 1, saidsystem having a high rate of discharge of thermal energy from itsthermal store, said thermal energy discharge rate being greater than acharging energy rate of the system.
 6. The system of claim 1, whereinthe heat exchanger includes a core that allows production of volumes ofhot water substantially greater than the volume of the system.
 7. Thesystem of claim 1, wherein hot water delivery volume is user-controlledthrough modifying temperature of the thermal store.
 8. The system ofclaim 1, wherein hot water delivery temperature is user-controlledthrough modifying a steam to cold water ratio in the system.
 9. Thesystem of claim 1, said system delivering water at user-selectable,above-input pressure through varying an amount of steam passed into anoutput reservoir.
 10. The system of claim 1, wherein the system outputcan be one of steam or hot water as selectable by a user.
 11. The systemof claim 1, wherein once it is charged the system provides hot waterwithout connection to a power supply until thermal energy held in thethermal store is depleted.
 12. The system of claim 1, the systemprovides steam without connection to a power supply until thermal energyheld in the thermal store is depleted.
 13. The system of claim 1,wherein operational temperature of the system is such that the system isinhospitable to bacteria such as Legionella.
 14. The system of claim 1,wherein the system is configured to recycle waste hot water through thesystem which reduces overall energy expended in heating a given amountof water.
 15. The system of claim 1, wherein the system is configured torecycle waste hot water through the system to reduce overall water usagefor a given overall throughput.